In the late 80s, early 90s, my room mates and I lived cheaply via dumpster diving in Boulder Colorado - NOT a community known for its frugality friendly cost of living. Since then Grocery stores sealed and locked their dumpsters, but back then, we mostly only visited one grocery store's dumpster, the Rudi's bakery's dumpster, and Willow river's (?) -a cheese company in Longmont- dumpster - we would get 5 lb blocks of cheese there that we sometimes had to cut a few mold spots off of, but mostly, were fine, just past that magic date. We always had cheddar, swiss, mozzarella, and munster on hand, and sometimes more exotic imported cheeses. Rudi's supplied so much bread we gave it away, after loading up the freezer. we only went there every few weeks. The grocery store dumpster was never gross. Bulk potatoes and onions, and fruit - if there was one rotten one, the whole 50 lb bag or crate wnt into the dumpster, frozen juice, if one leaks, they pitch the whole case, as they aren't allowed to wash the cans...the list goes on. Obviously meat, unless they were just walking it out and handed it to us, no go. But I think the only thing we routinely spent money on was tea, coffee, milk, butter and olive oil, though sometimes those were found. The key with the bulk veggies and fruit - always go through the whole bag/box when you get home to get rid of the "bad apple", wash it if it was in contact with the bad one, and you should be good to go.
I've since moved to a smaller Illinois town and am somewhat higher profile here, so that's over for now, though I have been thinking of driving down the highway to Indy, where I can dive in complete anonymity. :)
Oh, and also, all the furniture, building supplies I'v found in dumpsters and alleys. We used tohit all the frat/sorority and dorm dumpsters after the summer semester. So much brand new and almost new stuff, including clothes. I still use an iron found brand new in box that way, and still have a north face down jacket and shell found ON a frat dumpster.
Dumpsters - other peoples off-casts in general are great!
